Fluid valves having throttling elements actuated by sliding stems are generally known in the art for regulating fluid flow in process control systems. These fluid valves may include control valves and regulators. The fluid valves are typically coupled to an actuator, which may generate force hydraulically, pneumatically, or electrically. In the case of actuator failure, a manually operated hand jack may be used to move a valve stem assembly so that a throttling element is placed in a safe open or closed position under emergency conditions. Previously known hand jacks may include a bracket, a lever, a pivot pin, and a rod. A handwheel may be attached to the rod to facilitate application of manual torsion force to the rod. Rotation of the rod may pivot the lever about the pin. The lever engages a valve stem, the actuator, or some other component of the valve stem assembly such that rotation of the lever raises or lowers the valve stem, thus opening or closing the valve.
Conventional hand jacks may disadvantageously generate unwanted friction and bending forces during operation. As the lever pivots from an open to close position or close to open position, a point at which the rod is coupled to the lever may follow a generally arcuate path. The bracket usually engages another portion of the rod such that the rod is held in a substantially constant attitude with respect to the valve stem. With one portion of the rod substantially in place and a free end of the rod movable through an arcuate path, operation of the hand jack causes significant bending forces on the rod. The bending forces at the rod/lever coupling thereby increase friction during operation and therefore the force required to operate the hand jack. These stresses on the rod may also magnify the load on coupling mechanisms, e.g., mounting bolts, that secure the hand jack to the valve, and may increase the wear and tear on the device. Moreover, the load on the mounting bolts may increase the risk of structural failure.